HEATH 4552 OSCOPE WITH ONLY ONE CHANNEL WORKING, looking for the schematic

[Tank Circuit]

I have an old 25mhz Heath 4552 oscilloscope that I want to get running properly so I can sell it. Everything appears to be working except Channel A. When I select that input the trace never shows up. It seems as if the vertical position is slammed off the screen since there is a slight glow that can be seen if the room is dark.

I have several other 100mhz scopes and I plan on using one of them to isolate this problem. It would make this a great deal easier if I had the schematic. I noticed some time ago someone had a power supply issue with the same model oscilloscope and a member sent him that section of the schematic from a service manual. I was wondering if someone might have the rest of that manual.

I did see a couple of sites that would sell me a copy, and if I was fixing it for my lab I would go that route, but since I have a new 200mhz digital storage scope on the way, I don't want to spend any money on this one. Heck, if the price to fix this one is too much, I will sell it as-is for about $20.

[Tank Circuit]

Re: HEATH 4552 OSCOPE WITH ONLY ONE CHANNEL WORKING, looking for the schematic

Found it:
https://drive.google.com/file/d/0B8K...c0QnAwbHM/view

Relabelled Heath from the manufacturer Pintek (model PS-251)

Operating manual:


Pintek specs can be found here:
http://www.pintek.com.tw/

The most important find is this video (where I got most of the details I have listed) of the exact model being calibrated step by step. w2aew rules the oscilloscope world!
https://www.youtube.com/watch?v=SsoAe0kMYfc

[redwire]

Re: HEATH 4552 OSCOPE WITH ONLY ONE CHANNEL WORKING, looking for the schematic

It's good you found the schematic. It is the same (rebadged) as other scopes such as B&K Precision 2120.

The input amp might be damaged, or the deflection amp shorted so the beam is way up high or down low.
You would have to check the DC balance starting at the LF13741 input op-amp and working your way to the CRT.

[stj]

Re: HEATH 4552 OSCOPE WITH ONLY ONE CHANNEL WORKING, looking for the schematic

if your lucky the chips AND transistors will be in sockets - and you can just swap them between channels to test them.